feat: drop support of Python 3.8

[huxuan]

Pull Request Checklist

• A news fragment is added in news/ describing what is new.
• Test cases added for changed code.

Describe what you have changed in this PR.

Fix #3287

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.32%. Comparing base (d1dc03d) to head (560e81f).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3298      +/-   ##
==========================================
- Coverage   85.33%   85.32%   -0.01%     
==========================================
  Files         112      112              
  Lines       11402    11396       -6     
  Branches     2487     2485       -2     
==========================================
- Hits         9730     9724       -6     
  Misses       1143     1143              
  Partials      529      529              

Flag	Coverage Δ
unittests	85.14% <100.00%> (+<0.01%)	⬆️

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[frostming]

Thank you